It specifies a HTTP URL which will return username&password which will
be used to authenticate access to the git repo.
This is mainly used for git repo accecpt dynamic password (for example
oauth bare token). Because the dynamic password might expire very soon,
so it's added to the main syncRepo loop.
Typical usage case is work with a sidecar called gce-node-auth on GKE,
it uses the GCE service account's oauth token as password to access
Cloud Source Repo.
Please see the repo below for how it worked.
https://github.com/cydu-cloud/gce-node-auth/blob/master/git-sync-with-gce-node-auth.yaml
Chuanying Du